feat: add Home page with user dashboard and habit tracking features

- Implemented Home component with user authentication and loading states.
- Created Welcome component for unauthenticated users with a sign-in option.
- Developed Dashboard component to display user's habits and progress.
- Added functionality for habit management, including adding, updating, and deleting habits.
- Integrated HabitChart and HabitHistory components for visual representation of habits.
- Introduced sharing functionality for progress via Discord integration.

feat: establish Discord sharing configuration and routes

- Added DiscordSharingConfig type and readDiscordSharingConfig function for environment variable management.
- Created sharing contracts for input validation and data structure.
- Implemented sharing routes for previewing and sending progress images to Discord.
- Added tests for sharing routes to ensure authentication and proper error handling.

.env.example

@@ -10,3 +10,7 @@ DISCORD_CLIENT_ID=
 DISCORD_CLIENT_SECRET=
 # Generate once: openssl rand -hex 32 (at least 32 characters required)
 AUTH_COOKIE_SECRET=
+# Bot-powered progress sharing. Invite the bot to the server and grant it
+# View Channel, Send Messages, and Attach Files in this channel.
+DISCORD_BOT_TOKEN=
+DISCORD_SHARING_CHANNEL_ID=